Media assisted valves are well known for controlling fluid flow under a variety of conditions and for a variety of purposes. For example, such a valve may be used as a pressure relief or safety valve. Available valves of the type of the invention often have a substantial number of parts which generally increases the cost of manufacture and assembly of the valve. Further, such valves frequently include internal operating parts which are more difficult and time consuming than the present invention to change for valve repair and are affected by temperature changes in the media being controlled, often precluding high temperature service. Some such valves utilize operating parts which include valve members not under positive control at all times during operation in both directions. The absence of structure for positive control in both directions may cause a valve to chatter.